HepMC Reference Documentation HepMC

GenVertex.cc

Go to the documentation of this file.

// Matt.Dobbs@Cern.CH, September 1999
// GenVertex within an event

#include "HepMC/GenParticle.h"
#include "HepMC/GenVertex.h"
#include "HepMC/GenEvent.h"
#include "HepMC/SearchVector.h"
#include <iomanip>       // needed for formatted output

namespace HepMC {

    GenVertex::GenVertex( const FourVector& position,
                          int id, const WeightContainer& weights ) 
        : m_position(position), m_id(id), m_weights(weights), m_event(0),
          m_barcode(0)
    {
        s_counter++;
    }

    GenVertex::GenVertex( const GenVertex& invertex ) 
    : m_position( invertex.position() ),
      m_particles_in(),
      m_particles_out(),
      m_id( invertex.id() ),
      m_weights( invertex.weights() ),
      m_event(0),
      m_barcode(0) 
    {
        //
        for ( particles_in_const_iterator 
                  part1 = invertex.particles_in_const_begin();
              part1 != invertex.particles_in_const_end(); ++part1 ) {
            if ( !(*part1)->production_vertex() ) { 
                GenParticle* pin = new GenParticle(**part1);
                add_particle_in(pin);
            }
        }
        for ( particles_out_const_iterator
                  part2 = invertex.particles_out_const_begin();
              part2 != invertex.particles_out_const_end(); part2++ ) {
            GenParticle* pin = new GenParticle(**part2);
            add_particle_out(pin);
        }
        suggest_barcode( invertex.barcode() );
        //
        s_counter++;
    }
    
    GenVertex::~GenVertex() {
        //
        // need to delete any particles previously owned by this vertex
        if ( parent_event() ) parent_event()->remove_barcode(this);
        delete_adopted_particles();
        s_counter--;
    }

    void GenVertex::swap( GenVertex & other)
    {
        m_position.swap( other.m_position );
        m_particles_in.swap( other.m_particles_in );
        m_particles_out.swap( other.m_particles_out );
        std::swap( m_id, other.m_id );
        m_weights.swap( other.m_weights );
        std::swap( m_event, other.m_event );
        std::swap( m_barcode, other.m_barcode );
    }

    GenVertex& GenVertex::operator=( const GenVertex& invertex ) {

        // best practices implementation
        GenVertex tmp( invertex );
        swap( tmp );
        return *this;
    }
    
    bool GenVertex::operator==( const GenVertex& a ) const {
        //
        if ( a.position() !=  this->position() ) return 0;
        // if the size of the inlist differs, return false.
        if ( a.particles_in_size() !=  this->particles_in_size() ) return 0;
        // if the size of the outlist differs, return false.
        if ( a.particles_out_size() !=  this->particles_out_size() ) return 0;
        // loop over the inlist and ensure particles are identical
        //   (only do this if the lists aren't empty - we already know
        //   if one isn't, then other isn't either!)
        if ( a.particles_in_const_begin() != a.particles_in_const_end() ) {
            for ( GenVertex::particles_in_const_iterator 
                      ia = a.particles_in_const_begin(),
                      ib = this->particles_in_const_begin();
                  ia != a.particles_in_const_end(); ia++, ib++ ){
                if ( **ia != **ib ) return 0;
            }
        }
        // loop over the outlist and ensure particles are identical
        //   (only do this if the lists aren't empty - we already know
        //   if one isn't, then other isn't either!)
        if ( a.particles_out_const_begin() != a.particles_out_const_end() ) {
            for ( GenVertex::particles_out_const_iterator 
                      ia = a.particles_out_const_begin(),
                      ib = this->particles_out_const_begin();
                  ia != a.particles_out_const_end(); ia++, ib++ ){
                if ( **ia != **ib ) return 0;
            }
        }
        return 1;
    }

    bool GenVertex::operator!=( const GenVertex& a ) const {
        // Returns true if the positions and lists of a and this are not equal.
        return !( a == *this );
    }  

    void GenVertex::print( std::ostream& ostr ) const {
        if ( barcode()!=0 ) {
            if ( position() != FourVector(0,0,0,0) ) {
                ostr << "Vertex:";
                ostr.width(9);
                ostr << barcode();
                ostr << " ID:";
                ostr.width(5);
                ostr << id();
                ostr << " (X,cT)=";
                ostr.width(9);
                ostr.precision(2);
                ostr.setf(std::ios::scientific, std::ios::floatfield);
                ostr.setf(std::ios_base::showpos);
                ostr << position().x() << ",";
                ostr.width(9);
                ostr.precision(2);
                ostr << position().y() << ",";
                ostr.width(9);
                ostr.precision(2);
                ostr << position().z() << ",";
                ostr.width(9);
                ostr.precision(2);
                ostr << position().t();
                ostr.setf(std::ios::fmtflags(0), std::ios::floatfield);
                ostr.unsetf(std::ios_base::showpos);
                ostr << std::endl;
            } else {
                ostr << "GenVertex:";
                ostr.width(9);
                ostr << barcode();
                ostr << " ID:";
                ostr.width(5);
                ostr << id();
                ostr << " (X,cT):0";
                ostr << std::endl;
            }
        } else {
            // If the vertex doesn't have a unique barcode assigned, then
            //  we print its memory address instead... so that the
            //  print out gives us a unique tag for the particle.
            if ( position() != FourVector(0,0,0,0) ) {
                ostr << "Vertex:";
                ostr.width(9);
                ostr << (void*)this;
                ostr << " ID:";
                ostr.width(5);
                ostr << id();
                ostr << " (X,cT)=";
                ostr.width(9);
                ostr.precision(2);
                ostr.setf(std::ios::scientific, std::ios::floatfield);
                ostr.setf(std::ios_base::showpos);
                ostr << position().x();
                ostr.width(9);
                ostr.precision(2);
                ostr << position().y();
                ostr.width(9);
                ostr.precision(2);
                ostr << position().z();
                ostr.width(9);
                ostr.precision(2);
                ostr << position().t();
                ostr.setf(std::ios::fmtflags(0), std::ios::floatfield);
                ostr.unsetf(std::ios_base::showpos);
                ostr << std::endl;
            } else {
                ostr << "GenVertex:";
                ostr.width(9);
                ostr << (void*)this;
                ostr << " ID:";
                ostr.width(5);
                ostr << id();
                ostr << " (X,cT):0";
                ostr << std::endl;
            }
        }

        // print the weights if there are any
        if ( ! weights().empty() ) {
            ostr << " Wgts(" << weights().size() << ")=";
            for ( WeightContainer::const_iterator wgt = weights().begin();
                  wgt != weights().end(); wgt++ ) { ostr << *wgt << " "; }
            ostr << std::endl;
        }
        // print out all the incoming, then outgoing particles
        for ( particles_in_const_iterator part1 = particles_in_const_begin();
              part1 != particles_in_const_end(); part1++ ) {
            if ( part1 == particles_in_const_begin() ) {
                ostr << " I:";
                ostr.width(2);
                ostr << m_particles_in.size();
            } else { ostr << "     "; }
            //(*part1)->print( ostr );  //uncomment for long debugging printout
            ostr << **part1 << std::endl;
        }
        for ( particles_out_const_iterator part2 = particles_out_const_begin();
              part2 != particles_out_const_end(); part2++ ) {
            if ( part2 == particles_out_const_begin() ) { 
                ostr << " O:";
                ostr.width(2);
                ostr << m_particles_out.size();
            } else { ostr << "     "; }
            //(*part2)->print( ostr ); // uncomment for long debugging printout
            ostr << **part2 << std::endl;
        }
    }

    double GenVertex::check_momentum_conservation() const {
        double sumpx = 0, sumpy = 0, sumpz = 0;
        for ( particles_in_const_iterator part1 = particles_in_const_begin();
              part1 != particles_in_const_end(); part1++ ) {
            sumpx   += (*part1)->momentum().px();
            sumpy   += (*part1)->momentum().py();
            sumpz   += (*part1)->momentum().pz();
        }
        for ( particles_out_const_iterator part2 = particles_out_const_begin();
              part2 != particles_out_const_end(); part2++ ) {
            sumpx   -= (*part2)->momentum().px();
            sumpy   -= (*part2)->momentum().py();
            sumpz   -= (*part2)->momentum().pz();
        }
        return sqrt( sumpx*sumpx + sumpy*sumpy + sumpz*sumpz );
    }

    void GenVertex::add_particle_in( GenParticle* inparticle ) {
        if ( !inparticle ) return;
        // if inparticle previously had a decay vertex, remove it from that
        // vertex's list
        if ( inparticle->end_vertex() ) {
            inparticle->end_vertex()->remove_particle_in( inparticle );
        }
        m_particles_in.push_back( inparticle );
        inparticle->set_end_vertex_( this );
    }

    void GenVertex::add_particle_out( GenParticle* outparticle ) {
        if ( !outparticle ) return;
        // if outparticle previously had a production vertex,
        // remove it from that vertex's list
        if ( outparticle->production_vertex() ) {
            outparticle->production_vertex()->remove_particle_out( outparticle );
        }
        m_particles_out.push_back( outparticle );
        outparticle->set_production_vertex_( this );
    }

    GenParticle* GenVertex::remove_particle( GenParticle* particle ) {
        if ( !particle ) return 0;
        if ( particle->end_vertex() == this ) {
            particle->set_end_vertex_( 0 );
            remove_particle_in(particle);
        }
        if ( particle->production_vertex() == this ) {
            particle->set_production_vertex_(0);
            remove_particle_out(particle);
        }
        return particle;
    }

    void GenVertex::remove_particle_in( GenParticle* particle ) {
        if ( !particle ) return;
        m_particles_in.erase( already_in_vector( &m_particles_in, particle ) );
    }

    void GenVertex::remove_particle_out( GenParticle* particle ) {
        if ( !particle ) return;
        m_particles_out.erase( already_in_vector( &m_particles_out, particle ) );
    }

    void GenVertex::delete_adopted_particles() {
        //
        if ( m_particles_out.empty() && m_particles_in.empty() ) return;
        // 1. delete all outgoing particles which don't have decay vertices.
        //    those that do become the responsibility of the decay vertex
        //    and have their productionvertex pointer set to NULL
        for ( std::vector<GenParticle*>::iterator part1 = m_particles_out.begin();
              part1 != m_particles_out.end(); ) {
            if ( !(*part1)->end_vertex() ) {
                delete *(part1++);
            } else { 
                (*part1)->set_production_vertex_(0);
                ++part1;
            }
        }
        m_particles_out.clear();
        //
        // 2. delete all incoming particles which don't have production
        //    vertices. those that do become the responsibility of the 
        //    production vertex and have their decayvertex pointer set to NULL
        for ( std::vector<GenParticle*>::iterator part2 = m_particles_in.begin();
              part2 != m_particles_in.end(); ) {
            if ( !(*part2)->production_vertex() ) { 
                delete *(part2++);
            } else { 
                (*part2)->set_end_vertex_(0); 
                ++part2;
            }
        }
        m_particles_in.clear();
    }

    bool GenVertex::suggest_barcode( int the_bar_code )
    {
        if ( the_bar_code >0 ) {
            std::cerr << "GenVertex::suggest_barcode WARNING, vertex bar codes"
                      << "\n MUST be negative integers. Positive integers "
                      << "\n are reserved for particles only. Your suggestion "
                      << "\n has been rejected." << std::endl;
            return false;
        }
        bool success = false;
        if ( parent_event() ) {
            success = parent_event()->set_barcode( this, the_bar_code );
        } else { set_barcode_( the_bar_code ); }
        return success;
    }

    void GenVertex::set_parent_event_( GenEvent* new_evt ) 
    { 
        GenEvent* orig_evt = m_event;
        m_event = new_evt; 
        //
        // every time a vertex's parent event changes, the map of barcodes
        //   in the new and old parent event needs to be modified to 
        //   reflect this
        if ( orig_evt != new_evt ) {
            if (new_evt) new_evt->set_barcode( this, barcode() );
            if (orig_evt) orig_evt->remove_barcode( this );
            // we also need to loop over all the particles which are owned by 
            //  this vertex, and remove their barcodes from the old event.
            for ( particles_in_const_iterator part1=particles_in_const_begin();
                  part1 != particles_in_const_end(); part1++ ) {
                if ( !(*part1)->production_vertex() ) { 
                    if ( orig_evt ) orig_evt->remove_barcode( *part1 );
                    if ( new_evt ) new_evt->set_barcode( *part1, 
                                                         (*part1)->barcode() );
                }
            }
            for ( particles_out_const_iterator
                      part2 = particles_out_const_begin();
                  part2 != particles_out_const_end(); part2++ ) {
                    if ( orig_evt ) orig_evt->remove_barcode( *part2 );
                    if ( new_evt ) new_evt->set_barcode( *part2, 
                                                         (*part2)->barcode() );
            }
        }
    }

    // Static  //
    unsigned int GenVertex::counter() { return s_counter; }
    unsigned int GenVertex::s_counter = 0; 

    // Friends //

    std::ostream& operator<<( std::ostream& ostr, const GenVertex& vtx ) {
        if ( vtx.barcode()!=0 ) ostr << "BarCode " << vtx.barcode();
        else ostr << "Address " << &vtx;
        ostr << " (X,cT)=";
        if ( vtx.position() != FourVector(0,0,0,0)) {
            ostr << vtx.position().x() << ","
                 << vtx.position().y() << ","
                 << vtx.position().z() << ","
                 << vtx.position().t();
        } else { ostr << 0; }
        ostr << " #in:" << vtx.particles_in_size()
             << " #out:" << vtx.particles_out_size();
        return ostr;
    }

    // edge_iterator           // (protected - for internal use only)
    // If the user wants the functionality of the edge_iterator, he should
    // use particle_iterator with IteratorRange = family, parents, or children
    //

    GenVertex::edge_iterator::edge_iterator() : m_vertex(0), m_range(family), 
        m_is_inparticle_iter(0), m_is_past_end(1)
    {}

    GenVertex::edge_iterator::edge_iterator( const GenVertex& vtx, 
                                          IteratorRange range ) :
        m_vertex(&vtx), m_range(family) 
    {
        // Note: (26.1.2000) the original version of edge_iterator inheritted
        //       from set<GenParticle*>::const_iterator() rather than using
        //       composition as it does now.
        //       The inheritted version suffered from a strange bug, which
        //       I have not fully understood --- it only occurred after many
        //       events were processed and only when I called the delete 
        //       function on past events. I believe it had something to do with
        //       the past the end values, which are now robustly coded in this
        //       version as boolean members.
        //
        // default range is family, only other choices are children/parents
        //    descendants/ancestors not allowed & recasted ot children/parents
        if ( range == descendants || range == children ) m_range = children;
        if ( range == ancestors   || range == parents  ) m_range = parents;
        //
        if ( m_vertex->m_particles_in.empty() &&
             m_vertex->m_particles_out.empty() ) {
            // Case: particles_in and particles_out is empty.
            m_is_inparticle_iter = 0;
            m_is_past_end = 1;
        } else if ( m_range == parents && m_vertex->m_particles_in.empty() ){
            // Case: particles in is empty and parents is requested.
            m_is_inparticle_iter = 1;
            m_is_past_end = 1;
        } else if ( m_range == children && m_vertex->m_particles_out.empty() ){
            // Case: particles out is empty and children is requested.
            m_is_inparticle_iter = 0;
            m_is_past_end = 1;
        } else if ( m_range == children ) {
            // Case: particles out is NOT empty, and children is requested
            m_set_iter = m_vertex->m_particles_out.begin();
            m_is_inparticle_iter = 0;
            m_is_past_end = 0;
        } else if ( m_range == family && m_vertex->m_particles_in.empty() ) {
            // Case: particles in is empty, particles out is NOT empty,
            //       and family is requested. Then skip ahead to partilces out.
            m_set_iter = m_vertex->m_particles_out.begin();
            m_is_inparticle_iter = 0;
            m_is_past_end = 0;
        } else {
            // Normal scenario: start with the first incoming particle
            m_set_iter = m_vertex->m_particles_in.begin();
            m_is_inparticle_iter = 1;
            m_is_past_end = 0;
        }
    }

    GenVertex::edge_iterator::edge_iterator( const edge_iterator& p ) {
        *this = p;
    }

    GenVertex::edge_iterator::~edge_iterator() {}

    GenVertex::edge_iterator& GenVertex::edge_iterator::operator=(
        const edge_iterator& p ) {
        m_vertex = p.m_vertex;
        m_range = p.m_range;
        m_set_iter = p.m_set_iter;
        m_is_inparticle_iter = p.m_is_inparticle_iter;
        m_is_past_end = p.m_is_past_end;
        return *this;
    }

    GenParticle* GenVertex::edge_iterator::operator*(void) const {
        if ( !m_vertex || m_is_past_end ) return 0;
        return *m_set_iter;
    }

    GenVertex::edge_iterator& GenVertex::edge_iterator::operator++(void){
        // Pre-fix increment
        //
        // increment the set iterator (unless we're past the end value)
        if ( m_is_past_end ) return *this;
        ++m_set_iter;
        // handle cases where m_set_iter points past the end
        if ( m_range == family && m_is_inparticle_iter &&
             m_set_iter == m_vertex->m_particles_in.end() ) {
            // at the end on in particle set, and range is family, so move to
            // out particle set
            m_set_iter = m_vertex->m_particles_out.begin();
            m_is_inparticle_iter = 0;
        } else if ( m_range == parents && 
                    m_set_iter == m_vertex->m_particles_in.end() ) {
            // at the end on in particle set, and range is parents only, so
            // move into past the end state
            m_is_past_end = 1;
        } 
        // the following is not else if because we might have range=family
        // with an empty particles_out set.     
        if ( m_set_iter == m_vertex->m_particles_out.end() ) {
            //whenever out particles end is reached, go into past the end state
            m_is_past_end = 1;
        }
        return *this;
    }

    GenVertex::edge_iterator GenVertex::edge_iterator::operator++(int){
        // Post-fix increment
        edge_iterator returnvalue = *this;
        ++*this;
        return returnvalue;
    }

    bool GenVertex::edge_iterator::is_parent() const {
        if ( **this && (**this)->end_vertex() == m_vertex ) return 1;
        return 0;
    }

    bool GenVertex::edge_iterator::is_child() const {
        if ( **this && (**this)->production_vertex() == m_vertex ) return 1;
        return 0;
    }

    int GenVertex::edges_size( IteratorRange range ) const {
        if ( range == children ) return m_particles_out.size();
        if ( range == parents ) return m_particles_in.size();
        if ( range == family ) return m_particles_out.size()
                                      + m_particles_in.size();
        return 0;
    }

    // vertex_iterator //
    
    GenVertex::vertex_iterator::vertex_iterator() 
        : m_vertex(0), m_range(), m_visited_vertices(0), m_it_owns_set(0), 
          m_recursive_iterator(0)
    {}

    GenVertex::vertex_iterator::vertex_iterator( GenVertex& vtx_root,
                                              IteratorRange range )
        : m_vertex(&vtx_root), m_range(range) 
    {
        // standard public constructor
        //
        m_visited_vertices = new std::set<const GenVertex*>;
        m_it_owns_set = 1;
        m_visited_vertices->insert( m_vertex );
        m_recursive_iterator = 0;
        m_edge = m_vertex->edges_begin( m_range );
        // advance to the first good return value
        if ( !follow_edge_() &&
             m_edge != m_vertex->edges_end( m_range )) ++*this;
    }

    GenVertex::vertex_iterator::vertex_iterator( GenVertex& vtx_root,
        IteratorRange range, std::set<const HepMC::GenVertex*>& visited_vertices ) :
        m_vertex(&vtx_root), m_range(range), 
        m_visited_vertices(&visited_vertices), m_it_owns_set(0),
        m_recursive_iterator(0) 
    {
        // This constuctor is only to be called internally by this class
        //   for use with its recursive member pointer (m_recursive_iterator).
        // Note: we do not need to insert m_vertex_root in the vertex - that is
        //  the responsibility of this iterator's mother, which is normally
        //  done just before calling this protected constructor.
        m_edge = m_vertex->edges_begin( m_range );
        // advance to the first good return value
        if ( !follow_edge_() &&
             m_edge != m_vertex->edges_end( m_range )) ++*this;
     }

    GenVertex::vertex_iterator::vertex_iterator( const vertex_iterator& v_iter)
        : m_vertex(0), m_visited_vertices(0), m_it_owns_set(0), 
          m_recursive_iterator(0) 
    {
        *this = v_iter;
    }

    GenVertex::vertex_iterator::~vertex_iterator() {
        if ( m_recursive_iterator ) delete m_recursive_iterator;
        if ( m_it_owns_set ) delete m_visited_vertices;
    }

    GenVertex::vertex_iterator& GenVertex::vertex_iterator::operator=( 
        const vertex_iterator& v_iter ) 
    {
        // Note: when copying a vertex_iterator that is NOT the owner
        // of its set container, the pointer to the set is copied. Beware!
        // (see copy_with_own_set() if you want a different set pointed to)
        // In practise the user never needs to worry
        // since such iterators are only intended to be used internally.
        //
        // destruct data member pointers
        if ( m_recursive_iterator ) delete m_recursive_iterator;
        m_recursive_iterator = 0;
        if ( m_it_owns_set ) delete m_visited_vertices;
        m_visited_vertices = 0;
        m_it_owns_set = 0;
        // copy the target vertex_iterator to this iterator 
        m_vertex = v_iter.m_vertex;
        m_range = v_iter.m_range;
        if ( v_iter.m_it_owns_set ) {
            // i.e. this vertex will own its set if v_iter points to any
            // vertex set regardless of whether v_iter owns the set or not!
            m_visited_vertices = 
                new std::set<const GenVertex*>(*v_iter.m_visited_vertices);
            m_it_owns_set = 1;
        } else {
            m_visited_vertices = v_iter.m_visited_vertices;
            m_it_owns_set = 0;
        }
        //
        // Note: m_vertex_root is already included in the set of 
        //  tv_iter.m_visited_vertices, we do not need to insert it.
        //
        m_edge = v_iter.m_edge;
        copy_recursive_iterator_( v_iter.m_recursive_iterator );
        return *this;
    }

    GenVertex* GenVertex::vertex_iterator::operator*(void) const {
        // de-reference operator
        //
        // if this iterator has an iterator_node, then we return the iterator
        // node.
        if ( m_recursive_iterator ) return  **m_recursive_iterator;
        //
        // an iterator can only return its m_vertex -- any other vertex
        //  is returned by means of a recursive iterator_node 
        //  (so this is the only place in the iterator code that a vertex 
        //   is returned!) 
        if ( m_vertex ) return m_vertex;
        return 0;
    }

    GenVertex::vertex_iterator& GenVertex::vertex_iterator::operator++(void) {
        // Pre-fix incremental operator
        //
        // check for "past the end condition" denoted by m_vertex=0
        if ( !m_vertex ) return *this;
        // if at the last edge, move into the "past the end condition"
        if ( m_edge == m_vertex->edges_end( m_range ) ) {
            m_vertex = 0;
            return *this;
        }
        // check to see if we need to create a new recursive iterator by
        // following the current edge only if a recursive iterator doesn't
        // already exist. If a new recursive_iterator is created, return it.
        if ( follow_edge_() ) {
              return *this;
        }
        //
        // if a recursive iterator already exists, increment it, and return its
        // value (unless the recursive iterator has null root_vertex [its
        // root vertex is set to null if it has already returned its root] 
        // - in which case we delete it) 
        // and return the vertex pointed to by the edge.
        if ( m_recursive_iterator ) {
            ++(*m_recursive_iterator);
            if ( **m_recursive_iterator ) {
                return *this;
            } else {
                delete m_recursive_iterator;
                m_recursive_iterator = 0;
            }
        }
        //
        // increment to the next particle edge
        ++m_edge;
        // if m_edge is at the end, then we have incremented through all
        // edges, and it is time to return m_vertex, which we accomplish
        // by returning *this
        if ( m_edge == m_vertex->edges_end( m_range ) ) return *this;
        // otherwise we follow the current edge by recursively ++ing.
        return ++(*this);
    }

    GenVertex::vertex_iterator GenVertex::vertex_iterator::operator++(int) {
        // Post-fix increment
        vertex_iterator returnvalue(*this);
        ++(*this);
        return returnvalue;
    }

    void GenVertex::vertex_iterator::copy_with_own_set( 
        const vertex_iterator& v_iter, 
        std::set<const HepMC::GenVertex*>& visited_vertices ) {
        //
        // destruct data member pointers
        if ( m_recursive_iterator ) delete m_recursive_iterator;
        m_recursive_iterator = 0;
        if ( m_it_owns_set ) delete m_visited_vertices;
        m_visited_vertices = 0;
        m_it_owns_set = 0;
        // copy the target vertex_iterator to this iterator 
        m_vertex = v_iter.m_vertex;
        m_range = v_iter.m_range;
        m_visited_vertices = &visited_vertices;
        m_it_owns_set = 0;
        m_edge = v_iter.m_edge;
        copy_recursive_iterator_( v_iter.m_recursive_iterator );
    }

    GenVertex* GenVertex::vertex_iterator::follow_edge_() {
        // follows the edge pointed to by m_edge by creating a 
        // recursive iterator for it.
        //
        // if a m_recursive_iterator already exists, 
        // this routine has nothing to do,
        // if there's no m_vertex, there's no point following anything, 
        // also there's no point trying to follow a null edge.
        if ( m_recursive_iterator || !m_vertex || !*m_edge ) return 0;
        //
        // if the range is parents, children, or family (i.e. <= family)
        // then only the iterator which owns the set is allowed to create
        // recursive iterators (i.e. recursivity is only allowed to go one
        // layer deep)
        if ( m_range <= family && m_it_owns_set == 0 ) return 0;
        //
        // M.Dobbs 2001-07-16
        // Take care of the very special-rare case where a particle might
        // point to the same vertex for both production and end
        if ( (*m_edge)->production_vertex() == 
             (*m_edge)->end_vertex() ) return 0;
        //
        // figure out which vertex m_edge is pointing to
        GenVertex* vtx = ( m_edge.is_parent() ? 
                        (*m_edge)->production_vertex() :
                        (*m_edge)->end_vertex() );
        // if the pointed to vertex doesn't exist or has already been visited, 
        // then return null
        if ( !vtx || !(m_visited_vertices->insert(vtx).second) ) return 0;
        // follow that edge by creating a recursive iterator
        m_recursive_iterator = new vertex_iterator( *vtx, m_range,
                                                    *m_visited_vertices);
        // and return the vertex pointed to by m_recursive_iterator 
        return **m_recursive_iterator;
    }
        
    void GenVertex::vertex_iterator::copy_recursive_iterator_( 
        const vertex_iterator* recursive_v_iter ) {
        // to properly copy the recursive iterator, we need to ensure
        // the proper set container is transfered ... then do this 
        // operation .... you guessed it .... recursively!
        //
        if ( !recursive_v_iter ) return;
        m_recursive_iterator = new vertex_iterator();
        m_recursive_iterator->m_vertex = recursive_v_iter->m_vertex;
        m_recursive_iterator->m_range = recursive_v_iter->m_range;
        m_recursive_iterator->m_visited_vertices = m_visited_vertices;
        m_recursive_iterator->m_it_owns_set = 0;
        m_recursive_iterator->m_edge = recursive_v_iter->m_edge;
        m_recursive_iterator->copy_recursive_iterator_( 
            recursive_v_iter->m_recursive_iterator );
    }

    // particle_iterator         //

    GenVertex::particle_iterator::particle_iterator() {}

    GenVertex::particle_iterator::particle_iterator( GenVertex& vertex_root,
                                                     IteratorRange range ) {
        // General Purpose Constructor
        //
        if ( range <= family ) {
            m_edge = GenVertex::edge_iterator( vertex_root, range ); 
        } else {
            m_vertex_iterator = GenVertex::vertex_iterator(vertex_root, range);
            m_edge = GenVertex::edge_iterator( **m_vertex_iterator, 
                                                  m_vertex_iterator.range() ); 
        }
        advance_to_first_();
    }

    GenVertex::particle_iterator::particle_iterator( 
        const particle_iterator& p_iter ){
        *this = p_iter;
    }

    GenVertex::particle_iterator::~particle_iterator() {}

    GenVertex::particle_iterator& 
    GenVertex::particle_iterator::operator=( const particle_iterator& p_iter )
    {
        m_vertex_iterator = p_iter.m_vertex_iterator;
        m_edge = p_iter.m_edge;
        return *this;
    }

    GenParticle* GenVertex::particle_iterator::operator*(void) const {
        return *m_edge;
    }

    GenVertex::particle_iterator& 
    GenVertex::particle_iterator::operator++(void) {
        //Pre-fix increment 
        //
        if ( !*m_edge && !*m_vertex_iterator ) {
            // past the end condition: do nothing
            return *this;
        } else if ( !*m_edge && *m_vertex_iterator ) {
            // past end of edge, but still have more vertices to visit
            // increment the vertex, checking that the result is valid
            if ( !*(++m_vertex_iterator) ) return *this;
            m_edge = GenVertex::edge_iterator( **m_vertex_iterator, 
                                                  m_vertex_iterator.range() ); 
        } else {
            ++m_edge;
        }
        advance_to_first_();
        return *this;
    }

    GenVertex::particle_iterator GenVertex::particle_iterator::operator++(int){
        //Post-fix increment
        particle_iterator returnvalue(*this);
        ++(*this);
        return returnvalue;
    }

    GenParticle* GenVertex::particle_iterator::advance_to_first_() {
        if ( !*m_edge ) return *(++*this);
        // if the range is relatives, we need to uniquely assign each particle
        // to a single vertex so as to guarantee particles are returned
        // exactly once.
        if ( m_vertex_iterator.range() == relatives &&
             m_edge.is_parent() && 
             (*m_edge)->production_vertex() ) return *(++*this);
        return *m_edge;
    }

} // HepMC

---